When wells are drilled for production of petroleum products, well casing is inserted into the well bore and cemented in place to provide a durable, pressure containing lining for the well bore. For production of the petroleum products, such as crude oil, natural gas, and various mixtures thereof with other liquid such as water, one or more tubing strings are positioned within the well casing, typically being supported by a wellhead assembly. These tubing strings are sealed with respect to the wellhead such as by the connecting assemblies thereof and are also sealed downhole with respect to the casing by means of packers. Typically, through the use of packers, production zones for petroleum products are isolated in the well casing and the lower end of the tubing string is open to the production zone so that the petroleum products, flowing from the production zone into the well casing via perforations, may be conducted to the surface for production at the wellhead. Valve controlled flowlines extend from the wellhead to receiving lines for the petroleum products, often being passed through separators and other preliminary processing equipment for separating gases from liquids, for removing sand and other foreign matter contained in the well fluids, and perhaps also separating water and natural gas from the crude oil. If two or more production tubing strings are suspended within a well casing, typically these production strings terminate at different depths within the well bore and produce petroleum products from different production zones.
In order to facilitate selective downhole location of various well tools and to provide for location of completion equipment within a production tubing string, the tubing string is typically provided with internal completion profiles. These completion profiles are typically defined by tubing sections known as landing nipples or completion nipples. The corresponding well tool incorporates a section having a latch mechanism that is capable of entering the enlargements defined by the completion profiles and thus establishing a properly located and locked condition with respect to the tubing string. The latch mechanisms of well tools may be operated in any number of ways including mechanically, hydraulically, pneumatically, electrically, etc. The locking mechanism of the well tool is typically established at a set position at the time it enters the tubing string. After traversing the tubing string to an approximate depth, the latch mechanism is selectively actuated so that its latches expand into forcible engagement with the inside wall surface of the tubing string. Thereafter, the well tool is moved downwardly or upwardly to bring the latch mechanism into registry with the internal landing profile of the tubing string. When such registry has been established, the latch mechanism will then expand to its latched position and thus secure the well tool in a locked condition within the production string so that it can accomplish its desired purposes. Any number of different types of well tools such as well completion apparatus and well service tools, may be operatively positioned with respect to the tubing string in this manner. The well tools are capable of being removed from the tubing string by controllably actuating the latch mechanism to its unlatched position so that the well tool can be withdrawn through the tubing string by means of wireline equipment, by a coil tubing string, macaroni tubing string, etc.
Oil and gas fields in various portions of the earth's surface can have production conditions that facilitate fairly rapid build-up of foreign matter. For example, scale build-up within the production tubing has been common in the harsh well conditions of the gas fields that are located in the gulf of Thailand. This scale build-up must be periodically cleaned from the inside surface of the production tubing because it otherwise diminishes the flow capacity of the tubing and interferes with movement of well service and production tools through the tubing string.
Under severe conditions and high temperatures, production fluid contained materials such as barium sulfate, strontium sulphate and the like can become baked onto the inside of the production string such that the inside dimension of the production tubing is significantly reduced. These mineral deposits can become very hard and can be difficult to remove. For example, it is common for barium sulphate and strontium sulphate deposits to build up inside the tubing string and completion profiles to such an extent that total inside diameters of the production tubing are sometimes reduced by up to 25%, making most types of through tubing well servicing operations almost impossible. During such foreign matter build-up, the deposits of foreign matter also buildup inside the landing or completion profiles to such an extent that various well tools are not able to become properly seated and latched. Under this circumstance, it is desirable to provide a mechanism for not only cleaning the inside surface of the production tubing of undesirable production fluid mineral deposits and scale, but also cleaning such deposits from the completion profiles of the production tubing as well. It is also desirable that the reaming tool have the capability of cleaning the completion profiles of the production tubing without in any way distorting the critical configuration of the completion profiles. It is even further desirable to provide a cleaning tool for production tubing that is capable of sensing the location of a completion profile and cleaning it of any production fluid deposits so that it is returned to desired profile specifications for continued use.
When production tubing is installed within a well, especially where the tubing is deviated from the vertical to any extent, the inside dimension of the production tubing may not be to drift specifications. Thus it may be difficult or impossible to run well tools through the tubing string. It may be desirable to run a drift reamer through the production tubing while the reamer is being rotated, such as by means of a tubing supported downhole motor, to remove internal metal and slightly expand any tight spots in the production tubing to a minimum manufacturer's specification so that completion tools and well service tools may be efficiently passed through the production tubing without the possibility of "hanging up". This process is known in the industry as "drifting" the tubing. It is desirable, therefore, to provide a reaming tool for downhole production tubing which has the capability of accomplishing tubing drifting operations in addition to conducting other tubing cleaning operations as selected by the user.